Most ground source heating and cooling (GSHC) systems are unlikely to represent a risk to the environment from change the temperature in the ground around them, a study for the Government’s Chief Scientist has reported. However, larger GSHC systems or those in particular geological settings could have direct and indirect effects.
The study said that there are thought to be between 30,000 to 38,000 GSHC systems currently installed in the UK. Over the last decade, the average number of new installations a year has been 3,200 (increasing to 5,584 in 2022). It said historical trends and industry views indicated that the number of installations in the next 5 to 10 years is highly uncertain. But based on current and planned policy and trends there could be a jump in installations. It said future household-sized closed-loop installations (less than 45 kW) could be between 5,000 to 20,000 a year (currently about 2,000) and there could be more than 150 larger non-domestic installations (more than 100 kW) per year (currently about 60 to 80).
Most installations are closed-loop, but there could be a small increase from 16 to 30 open-loop installations per year.
The research aimed to help the Environment Agency and others understand where the environment is at greater or less risk of temperature changes in the ground around GSHC systems.
The project assessed the potential for temperature changes in the ground around GSHC systems of different sizes and in different geological settings, through a literature review and numerical modelling. The development of thermal plumes was simulated using flow, mass and heat transport modelling software.
The factors that have the greatest influence on thermal plume development are groundwater flow, bulk thermal conductivity and GSHC capacity (kW). Groundwater flowing past the GSHC system disperses the heat put into the ground; more groundwater flow results in a cooler but longer plume.